A model has been developed for the simultaneous heat and mass transfer during the ascension of superheated bubbles in a liquid column, allowing variable gas physical properties and bubble radius. A correction factor for isothermal gas hold-up correlations, based on bubble model results, has been derived in order to apply them to nonisothermal systems. Results for the bubble volume and the evaporated mass per bubble are used in the prediction of experimental data on gas hold-up and vaporization rate obtained in a direct contact evaporator with fairly good agreement. It has been shown that the constant property and constant bubble radius assumptions lead to overestimation of the vaporization rate and gas hold-up.